Film moving means in machine for reading bubble chamber photographs

ABSTRACT

A reading machine for bubble chamber photographs has a horizontal film table across which film is lengthwise advanced, frame by frame, from a supply reel at one side of the table to a takeup reel at the other side thereof, and to which the film is flatwise clamped for horizontal movement with the table. Carriers for the reels, extending below the table at opposite sides thereof, are mounted for motion transverse to film length and are driven in such motion in unison with the table to avoid twisting the film.

Feb. 6, 1973 United States Patent [191 Angelstrand et al.

[56] References Cited uNiTED'sTATEs'PATENr's 5/1967 Renold ......1.......2s'o/219 ux 8/1967 .....242/67.3 X 1/1968 Russell et all. 250/2l9 X trom, both of Jonkoping, Sweden 11968 A] [73] Assignee Saab Akfiebda! Linkcping! 6i1970 Sweden 22] Filed:

Primary Examiner-Stanley N. G-ilreath Assistant ExaminerWemer H. Schroeder Attorneylra Milton Jones Aug. 28, 1969 21 ApnLNo 854,147

Foreign Application Priority Data ABSTRACT A reading machine for bubble chamber photographs has a horizontal film table across which film is lengthwise advanced, frame by frame, from asupply reel at one side of the table to a takeup reel at the other side thereof, and to which the film is flatwise clamped for horizontal movement with the table. Carriers for the reels, extending below the table at opposite sides thereof, are mounted for motion transverse to film length and are driven in such motion in m n n l m 0 50 m x G 11 u 2 Mw m 022 m 7 W ,0 5 12 m 0. n 2 20 4 m %13 J n 7 h 6 4 d K 2 e 2 o 4 2 "7 m Two 8 u r a "a 1 m W W 2 C 0 d2 H S Ld A U IF l ll.

unison with the table to avoid twisting the film.

4 Claims, 6 Drawing Figures PATENTED FEB 6 I975 SHEET 2 OF 5 lNvzN'roRs Azzgelsirand B51" JQ'A Ragnar F'IG.Z.

ATTomNEb FILM MOVING MEANS IN MACHINE FOR READING BUBBLE CHAMBER PHOTOGRAPHS This invention relates generally to apparatus for scanning photographs of the tracks made by charged particles in a bubble chamber or cloud chamber for the purpose of converting the records contained on such photographs to a form that can be used by a computer and ultimately analyzed to provide infonnation about particle interactions and decays in nuclear physics experiments; and the invention relates more particularly to improvements in the portions of such apparatus that are concerned with movement of film to be scanned, comprising a film table and film reel carriers.

A bubble or cloud chamber, containing fluid in a condition of equilibrium between the liquid and gaseous states and surrounded by a super-conductive electromagnet, is a well known device used in nuclear physics experiments. When a charged particle is shot into the chamber, it leaves a track of tiny bubbles; and when it encounters another particle (which encounter is called an event) the particles taking part in the event trace branching tracks which diverge from the point of the encounter. These bubble tracks, although persisting only very briefly can be photographed stereoscopically to provide a record of the several paths taken by the particles involved in each event. Since the motions of the particles provide a clue to their natures, the study of photographic records of the branching or diverging tracks that denote events is of particular interest.

A reading machine of the type to which this invention relates is used to scan bubble chamber photographs for the purpose of converting the pictorial records of events to a form of data that can be stored in and used by an electronic computer. When a sufficient amount of such data is available, derived from the photographic records of numerous experiments, conclusions can be drawn, on the basis of statistical analysis of the data, about the nature and characteristics of the particles involved in the events being studied.

Inasmuch as valid conclusions can be drawn only on the basis of statistical study of a very large number of experiments, a tremendous amount of film needs to be analyzed truckloads, in many cases. Automation of the reading of the film records is therefore essential to reasonable management and utilization of the data contained in such records.

The film to be scanned or read is in the form of long strips, each having on it numerous lengthwise adjacent photographs or frames. For convenience, each strip is normally coiled on a reel or spool and is fed through the scanner or reading machine, frame by frame, from a supply reel to a takeup reel. Since each experiment is normally photographed by three cameras, focused along three coordinate axes, three related rolls of film are usually analyzed more or less simultaneously.

Each frame of film to be analyzed may contain one or more sets of diverging tracks that signify events, along with numerous other lines that trace the paths of particles that did not take part in events and which are therefore not of interest.

Selection of each part of a frame of film to be scanned isaccomplished, at least in part, with the aid of a human operator. As it scans the image on the film, the automatic reader produces signals corresponding to all tracks on the portion of the film being scanned. These signals are fed to a computer which in effect rejects signals corresponding to tracks not of interest and preserves data relating to events selected for analysis.

One type of information that the reading apparatus is required to obtain from the photographic record of an event is the exact location of the event in the bubble chamber space, as signified by the location on each photograph of the event of its vertex, that is, the junction of the diverging track lines which characterize the event. To obtain this data there must be provision in the machine for relative motion between the film and the scanning mechanism, so that the image of the vertex can be brought into exact coincidence with a defined axis of the scanning device, and the machine must also have measuring apparatus which is responsive to such motion to establish the location of the vertex by reference to a coordinate system in the machine that is related in a known manner to the coordinate system of the bubble chamber.

In one type of reading apparatus for bubble chamber photographs, disclosed in U.S. Pat. No. 3,366,794 to L. W. Alvarez, the scanning mechanism was made movable while the film was maintained stationary. However,

it is a premise of the present invention that the nature of the tracks to be analyzed is such that the most efficient and useful pattern of scanning is a spiral one in which the origin of the spiral is at the vertex that denotes an event.

The mechanism required for effecting a scan in a spiral pattern does not lend itself to translatory motion by which its optical axis could be moved relative to a stationary film.

Therefore it is a general object of the present invention to provide a reading machine of the character described which scans film in a spiral pattern and wherein the axis of the scanning mechanism remains stationary while the film is edgewise translated to bring the vertex of an event image thereon into coincidence with the axis of the scanning mechanism.

While reading machines have been proposed that provide for movement of the film relative to a stationary optical axis, they have not heretofore been completely successful, and it is thusanother general object of this invention to provide apparatus which avoids the problems and overcomes the difficulties that characterized prior reading machines in which the film was moved.

More specifically, the film being read in a machine with a fixed optical axis passes flatwise across a horizontal film table that is horizontally movable in all directions. The film is lengthwise advanced across the film table frame by frame, from a supply reel at one side of the film table to a takeup reel at the other side thereof, and as each frame to be scanned is brought into register with an aperture in the table, the portions of the film adjacent to that frame are clamped flatwise to the table so as to be constrained to move horizontally with the table. But movement of the table, and particularly its movements transverse to the length of the film strip, must not impose deforming stresses upon those portions of the film that extend from the table to the supply and takeup reels. One expedient heretofore proposed for avoiding the imposition of such undesired forces upon the film has been to arrange the film stretches just mentioned as rather large free loops, to take advantage of the inherent flexibility and suppleness of the film material; but such loops were obviously bulky and inconvenient, required care and attention when film was being threaded into the machine, and interfered with rapid feeding movement of film through the machine, thus imposing delays between the scannings of successive frames. Another prior proposal was to arrange the supply and takeup reels with their axes parallel to the direction of lengthwise movement of film through the film table, and to route the film stretches that extended between those reels and the film table over rollers that had their axes oblique to said direction; but this arrangement created difficulties when film was fed rapidly over the rollers.

By contrast with these prior arrangements, it is another general object of this invention to provide means in a machine of the character described for accommodating the bulky supply and takeup reels in a compact arrangement, and for causing all of the film on the machine to move with the film table in directions transverse to the length of the film so that the stretches of film which extend in opposite directions from the film table will at all times remain untwisted and therefore will not be subject to deformation or damage.

Another object of this invention is to provide carriers for the film supply and takeup reels in a reading machine of the character described, at opposite sides of a film table through which film extends from one of said reels to the other, and relatively simple and inexpensive mounting means for the heavy and bulky film carriers, providing ample support and guidance for them so that they can be readily moved in unison with the film table in directions transverse to the length of film extending therethrough.

With these observations and objects in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings. This disclosure is intended merely to exemplify the invention. The invention is not limited to the particular structure disclosed, and changes can be made therein which lie within the scope of the appended claims without departing from the invention.

The drawings illustrate two complete examples of physical embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which;

FIG. 1 is a general perspective view of reading apparatus embodying the principles of this invention;

FIG. 2 is a perspective view on a larger scale of the film moving mechanism of this invention;

FIG. 3 is a fragmentary perspective view, on a still larger scale, showing the means by which the film table is mounted for motion in opposite directions;

FIG. 4 is a more or less diagrammatic side elevation view of the film table and its carriage;

FIG. 5 is a plan view of the film table and its carriage, also somewhat diagrammatic, with portions shown broken away; and

FIG. 6 is a block diagram illustrating a modified form of apparatus embodying the principles of this invention.

Referring now more particularly to the accompanying drawings, the numeral 3 designates generally a reading machine in which the present invention is embodied, and FIG. 1 illustrates it in its relationship to apparatus with which it cooperates.

The film to be analyzed or read by means of the reading machine 3 is in the form of long strips, each divided along its length into a number of frames, and each frame usually containing a record of one or more events which are of interest. To facilitate handling, each strip is normally wound onto a reel 4 to form a roll. Inasmuch as each experiment in a bubble chamber is photographed simultaneously by three cameras, three related rolls of film must be read more or less simultaneously, to coordinate data for each frame in each roll with that for the corresponding frames in the other two rolls. The frames in each roll are successively numbered before the film is presented to the reading machine 3, to facilitate identification of the recorded events.

In FIG. 1, three related strips of film to be scanned by the reading machine are respectively designated 5, 6 and 7. They extend across a horizontal table 8 on the reading machine having three apertures 5a, 6a, 7a, one for each strip, that can be brought into alignment with a suitable light source (not shown) which is located beneath the table. Film transport means, comprising a suitable capstan drive 9, provides for lengthwise advancing the strips of film simultaneously across the table 8, to permit successive frames on each strip to be brought into register with the apertures in the table for the purpose of scanning. As described hereinafter, the film table is capable of bodily movement in all horizontal directions to permit any selected portion of a frame of film to be brought into alignment with the optical axis of an objective head 10 which is fixed above the film table and which comprises reflecting means.

The film table is provided with remotely controllable clamping means (not shown), which can be actuated magnetically or by vacuum and by which portions of each film strip that are adjacent to a frame registering with an aperture in the table can be releasably flatwise clamped to the table to compel the film to move with the table.

The image on the film frame that is under the objective head is projected up into the objective head, thence horizontally in one direction, and finally down onto the top surface of an operatorsv table 11. An obliquely disposed mirror 12 above the operator's table receives the image from the objective head and reflects it downwardly onto the operator's table.

The image is also projected from the objective head in the opposite horizontal direction, toward a half-silvered mirror 13, whence it is reflected downwardly into a scanning device 14. The image is also projected through the half-silvered mirror into a television camera 15 which receives only a very small portion of the total image on a film frame, corresponding to about a square milimeter of the film around the axis of the objective head. The image of this small area is presented to the operator, in very greatly magnified form, on the screen of a television receiver 16 that is connected with the television camera. This highly magnified portion of the total image is used for accurately locating the film table to bring the vertex of the event record to be studied into exact coincidence with the axis of the objective head and hence into coincidence with the scanning axis of the scanning device 14.

On the operators table there is a control console 17 for controlling film advance and the horizontal movements of the film table. The operator also has a typewriter 19 for input and output of data and an oscilloscope 20 that gives a graphic representation of light values measured during scanning.

The scanning device 14 is connected with an electronic computer 21 through an adaptor 22 which is in itselfa form of electronic computer.

Before a set of films is actually scanned or read, it is prescanned to store in the computing apparatus the numbers of those frames that record events of interest and the approximate locations on the frames of the vertices of such events. For the actual scanning operation, the computer so controls the film transport that each in turn of the frames to be studied is brought into register with the apertures in the film table. When a frame has thus been advanced into and locked in the film table, the computer makes a rough adjustment of the table, based on data obtained in the prescanning, and the operator makes the final adjustment by reference to the television receiver 16. Afterthe first frame is read, the computer automatically shifts the table to properly align with the optical axis the vertices on the corresponding frames of the other two strips of film.

Because film is dimensionally unstable, each frame of film has spaced apart fiducial marks, corresponding to fixed points in the photographed bubble chamber, and an accurate measurement of the distances between fiducial marks on a frame provides scale data and coordinate references for it from which events recorded thereon can be accurately located in the bubble chamber space. For feeding data into the computer concerning the coordinates of the fiducial marks on each frame, there is a fiducial plate 23 in front of the television camera that has specially shaped slots, and photomultipliers behind the slots register when the images of the fiducial marks align with these slots as the film table moves a frame horizontally. The signals from the photom ultipliers are combined with information derived from the table movements to produce information concerning the scale of the frame, which information is stored in the computer and used in conjunction with the signals obtained from the scanning of particle tracks that are recorded on the film.

Scanning can begin as soon as the vertex of an event record to be studied has been brought into coincidence with the optical axis.

The image of an event on a film frame is scanned in a spiral path, and hence the scanning apparatus is known as a spiral reader. The scanning begins at the vertex, progressing outwardly and around, and a signal is produced each time a track on the film record is crossed in the course of such scanning.

The scanning device 14 is described in the companion application of Sten Nordlund et al., Ser. No. 853,244, filed Aug. 27, 1969, now U.S. Pat. No. 3,512,883. Briefly, it comprises an elongated plane mirror and a periscope. The mirror is lengthwise inclined upwardly and outwardly relative to an axis about which it rotates so that as it moves orbitally it defines a reflecting cone and scans a strip-like portion of the film image that extends across a vertex near one of its ends and rotates around the vertex. The periscope is caused to rotate with the mirror, to have its eye always facing the mirror, and it moves steadily in a direction parallel to the axis of the mirror to scan along the rotating strip that the mirror reflects.

Data concerning the radial and angular coordinates of the spiral scan are continuously fed to the computer along with light signals produced each time a track is crossed in the course of scanning. After the record of a selected event on a frame of film has been scanned, records of the same event on the counterpart frames of the related strips of film are similarly scanned. Data from the three scannings of the event are combined by the computer into a form that defines an unambiguous three dimensional curve which characterizes the event, and this is stored in the computer to'be available for comparison with similarly obtained data for other events, for the purposes of statistical analysis.

From even the brief description of the scanning device that is given above, it will be evident that it would be feasible to move the scanning mechanism to bring its axis into coincidence with the image of a vertex on the film; and therefore the present invention contemplates bodily movement of the film table 8 to allow the film to be carried to a position where such coincidence exists. It will be appreciated that the portion of the film that is being scanned must be compelled to partake of all horizontal motion of the table and that the table must be moved with precision in order to insure that data concerning its movements will accurately depict the location of the vertex on the film.

The table is supported on the top of a frame structure 25 which, as shown, can comprise a cabinet that houses the scanning device 14. To carry the table for horizontal motion in Y-directions, transverse to the length of the film, there is a movable carriage 26 upon which the table is mounted and which rides on rails 27 and 28 on the frame structure that extend in the Y-directions. Rails 29 and 30 on the top of the carriage, extending in the X-directions, parallel to the length of the film, constrain the table to move with the carriage in the Y- directions but guide the table for X-direction motions relative to the carriage.

The upper surfaces of the rails 27 and 28 that support and guide the carriage 26 are horizontal and flat. They are engaged by carriage supporting rollers 31 that are journaled on the carriage for free rotation on horizontal axes. Guidance of the carriage forprecise linear motion in the Y-directions is provided by means of an upright longitudinal surface 32 on the rail 28, which surface is finished with special attention to insure that it will be accurately straight and flat and oriented exactly in the Y-directions. The surface 32 is engaged by rollers 33 on the carriage that haveupright shafts 34 which are fixed on the carriage at locations spaced apart in the Y-direction but which are laterally adjustable relative to the carriage.

The opposite upright surface 35 on the rail 28, which can be considered a reaction surface, is made reasonably straight and parallel to the master guide surface 32. The reaction surface is engaged by rollers 36 which likewise have upright shafts 37, but these are secured to the carriage in a manner described hereinafter to be biased for yielding reaction between the carriage and the surface 35 by which the carriage is urged in the direction to maintain the rollers 33 engaged with the master guide surface 32.

The shaft 34 for each of the rollers 33 that engage the master guide surface 32 is received in a blocklike holder 38 (see FIG. 3) that is rigidly secured to the carriage. Each shaft 34 has a cylindrical upper end portion which is received in its holder 38 and a lower rollerjournaling portion which is eccentric to its upper portion; hence rotation of the upper end portion 39 of the shaft carries the roller 33 for translatory adjustment relative to the carriage in the X-directions. To facilitate such adjustment each shaft can have a headed upper end portion 39 which projects above its holder and which is provided with a screw driver cross-slot. The block-like holder 38 in which each shaft is received can have a slot 40 that extends outwardly from its shaft receiving bore, and clamping screws 41 that extend transversely through the bifurcations defined by this slot can be tightened to hold the shaft in any position of rotational adjustment in which it may be established. The purpose of such adjustment of the shafts is to provide for so orienting the carriage that the X-direction table guide rail 29 thereon is exactly at right angle to the Y-direction carriage guide rail 28. Said angle being designated v in FIG. 5.

The shaft 37 for each roller 36 is received in a blocklike clamping holder 43, but instead of being rigidly secured to the carriage, each holder 43 is formed on the free end of one leg of a resilient substantially U- shaped spring member 42. The other leg of the spring member, and its bight portion, are secured to the carriage with the legs under convergent bias by which the roller 36 is urged toward the reaction surface 35. Preferably the shafts 37 for the rollers 36 are formed like the roller shafts 34, with eccentrically offset upper and lower portions, and the holders 4] are likewise formed as clamping membersvby which the shafts 37 can be held in any desired position of rotational adjustment. Such adjustment of the shafts 37 varies the biasing force which the rollers 36 exert against the reaction surface 35, allowing that force to be established at a value high enough to assure maintenance of engagement between the rollers 33 and the master guide surface 32 but not so high as to entail resistance to easy motion of the carriage when the rollers 36 pass over any high spots on the reaction surface 35.

The table is provided with rollers 44 which rotate on horizontal axes and which ride on the top surfaces of the rails 29 and 30 on the carriage, and is also provided with rollers that rotate on upright axes and cooperate with master and reaction surfaces formed on one of those rails. The arrangement of the rollers on the table can of course correspond to that of the rollers on the carriage.

Preferably the horizontal shafts for the rollers 31 and 44 which respectively support the carriage and the table are formed with eccentrically offset securement and journal portions to provide for adjustments that will assure accurately horizontal orientation and motion of the table.

The carriage is driven for movements in the Y- direction by means of a Y-drive motor 46 which is mounted on the frame structure 25 and which has its shaft coaxially coupled with a lead screw 47 that extends in the Y-direction and is confined against axial motion. The lead screw cooperates with a female threaded element 48 that is anchored on the carriage.

The table is similarly driven for X-direction movements relative to the carriage by means of an X-drive motor 49 that is mounted on the carriage and drives a coaxial lead screw 50 that extends in the X-direction.

The motors 46 and 49 are controllable from the operators console 17 as well as by the computer mechanisms. It will be understood that suitable transducers (not shown) are associated with the carriage and with the table, respectively, to feed to the computer mechanism signals denoting the magnitudes and directions of table movements, which signals are used in conjunction with the output of the scanning device.

Carriers 52 and 53 for the supply and takeup reels 4 are mounted at opposite sides of the frame structure 25, spaced from the table in the X-directions. Each carrier accommodates the reels for the three film strips 5, 6 and 7 being processed through the machine and is vertically elongated, extending downwardly a substantial distance along one side of the frame structure with its top at about the level of the table and its bottom a substantial distance below the level of the carriage rails 27 and 28.

The reels are supported in each reel carrier for rotation on axes that extend in the Y-direction. Inside the carrier each film strip extends from its reel in a downward loop through a so-called vacuum buffer 55, comprising loop level detecting vacuum operated switches 56 that control the rotation of the film reels in accordance with the rate of film advance effected by the capstan drive 9. From the vacuum buffer the film is trained over rollers 57 which guide it upwardly out of the carrier and horizontally partway toward the table, thence around the roller of the capstan drive and again horizontally to the table.

For proper guidance of the film within each reel carrier, the reel is constrained against axial motion relative to the reel carrier; but to avoid twisting of the film each reel carrier as a whole is bodily moved in the Y- directions in unison with Y-direction movements of the table.

Each reel carrier is mounted for such movement by means of a shaft 59 which extends in the Y-directions and which is supported on brackets 60 that project in wardly from the side surface of the reel carrier 52. Ball bushings 61 on the frame structure 25 surround the shaft to mount the reel carrier and the shaft for motion along the frame structure and also permit the reel carrier to swing freely about the axis of the shaft. Since the ball bushings 61 are located above the center of gravity of the reel carrier, and are spaced from its center of gravity in the direction toward the adjacent side of the frame structure, the bottom of the reel carrier tends to swing inwardly toward said side of the frame structure. The limit of such swinging motion is defined by a rail 62 on the side of the frame structure extending in the Y- directions, spaced at distance below the shaft 59 and having a flat outwardly facing surface, which surface is engaged by rollers 63 on the reel carrier. It will be evident that this mounting arrangement for each reel carrier provides for easy motion thereof in exactly the desired directions without involving manufacturing problems and complications.

Each reel carrier is constrained to move in unison with the table in the Y-directions by means of drive means for the reel carriers that are synchronized with the drive means by which the carriage 26 is moved. As shown in FIG. 2, there is a lead screw 65 for each reel carrier that extends in the Y-directions and is journaled in the frame structure and constrained to rotation.

Cooperating with each lead screw is a female threaded element or nut 66 that is so mounted on the reel carrier as to be confined against rotation but to constrain the reel carrier to move in unison with it in the Y-directions while providing for limited swinging motion of the reel carrier relative to it.

Each of the reel carrier driving lead screws 65 has a pulley 67 on its projecting outer end portion, and there is a double pulley 68 on the shaft of the Y'drive motor 46. Toothed belts 69 connect the driving pulley 68 with the respective pulleys 67 on the lead screws 65 and thus drive the reel carriers in the Y-directions in synchronism with Y-direction motion of the film table.

In the embodiment of the invention that is diagrammatically illustrated in FIG. 6, the reel carriers are driven by drive means separate from that which moves the film table, but control apparatus is provided for synchronizing motions of the reel carriers with movements of the film table. The arrangement illustrated in FIG. 6 is particularly useful where high speeds of film table movement are required. There may be one drive motor for both reel carriers or a separate drive motor for each reel carrier.

As illustrated in FIG. 6, the drive motor 46a for the film table is connected in a control circuit which includes an amplifier 70 and a position responsive trans ducer 71 from which there is a feedback connection 72 to a comparator 73. A program apparatus 74, which can be a part of the computer apparatus with which the scanning device is connected, produces output signals that define the positioning of the film table for each scanning operation. These output signals, which are produced on the basis of data previously fed into the program apparatus, are fed through a demand value line 75 to the comparator 73. The comparator, in a known manner, produces difference signals on the basis of a comparison of the demand value signals from the program apparatus with position signals from the transducer 71, fed to the comparator through the feedback connection 72. These difference signals are issued to the drive motor 46a through the amplifier 70, causing the drive motor to move the film table in such a manner as to bring the difference signal to zero, that is, to so position the film table as to satisfy the demand value.

The drive motor or motors 76 for the reel carriers are connected in a circuit comprising a comparator 77, an amplifier 78 through which signals from the comparator 77 are issued to the reel carrier drive means 76, and a detector 79 having a feedback connection 80 with the comparator and with supervisory circuit means 81. The detector 79 can be for example, an electrooptical or an electromechanical device, and it produces a signal which corresponds to the position difference in the Y- direction between the film table and the reel carrier or reel carriers operated by the drive means 76. The position difference with which the servo system is allowed to operate is determined by a reference value which is fed to the demand value input of the comparator 77. As long as the value of the feedback signal from the detector 79 exceeds this reference value the comparator issues signals to the drive means 76, through the amplifier 78, by which the drive means is caused to move the reel carriers in the direction to reduce the difference between the demand value signal and the feedback signal.

The supervisory circuit means 81 has an input from the program apparatus 74 and has an output 83 to the amplifier 78. Simultaneously with its issuance of a demand value signal to the film table drive motor 46a, the program apparatus issues an enabling signal to the amplifier 78 through the supervisory circuit means 81, which enabling signal starts the drive means 76. As the film table moves, the velocity and direction of the reel carrier drive means 76 will be controlled in response to the position difference feedback signal from the detector 79 so that the reel carriers will follow motion of the film table with a deviation determined by the reference value fed to the comparator 77.

When the film table drive motor 46a has moved the film table through the distance signified by the demand value signal, that motor stops. The reel carrier drive means 76 also stops provided the actual position difference between the reel carriers and the film table is then within the reference value; and if not, then the reel carrier drive means will continue in operation until the position difference is within that value. When both of the drive means 46a and 76 have stopped, the supervisory circuit means 81 delivers a receipt signal to the program apparatus 74 to prepare the latter for the next positioning of the movable units.

If at any time the position difference signal from the feedback line 80 exceeds a predetermined limit value, the supervisory circuit means 81 transmits a signal to the program apparatus 74 by which the velocity of the film table drive is reduced, to allow the reel carriers to catch up with it, or by which the film table and reel carrier servos are stopped as a precautionary measure.

From the foregoing description taken with the accompanying drawings it will be apparent that this invention provides a reading machine for bubble chamber photographs having means for controlledly moving film in all edgewise directions relative to the optical axis of a scanning mechanism and whereby such film movements can be effected with great rapidity and precision but without entailing twisting or other straining deformation of the film.

What is claimed as our invention is:

1. Apparatus for processing strip material having defined lengthwise adjacent frames, which apparatus comprises a horizontal table mounted for horizontal translatory motion in all directions and having a defined area with which a frame of strip material registers for processing, means for lengthwise advancing strip material flatwise across said area of the table from one to another of a pair of reels, and means for releasably constraining a portion of strip material that comprises a frame registering with said area to move with the table, said apparatus being characterized by:

A. a pair of reel carriers, one for each reel;

B. means supporting the table and the reel carriers with the table elevated and with the reel carriers extending downwardly to a level substantially below that of the table and spaced to opposite sides of the table so that the table and the reel carriers are spaced apart in directions parallel to that 3,715 ,086 l l 12 of strip advance, said supporting means providing straining the reel carriers to move with the table comfor prises: 1. horizontal translatory motion of the table in all A. three lead screws, each constrained to rotation directions,

2. rotation of the reels on horizontal axes transverse .to said direction of strip advance, and

3. translatory motion of the reel carriers in opposite directions parallel to said axes; and

and each extending parallel to said axes;

B. a nut connected with the table to move therewith in the directions of said axes and cooperating with one of said lead screws to impart motion to the table in said directions in consequence of rotation of said one lead screw;

C. a nut member carried by each of said reel carriers, each of said nut members being constrained to move with its reel carrier in the directions of said axes but being free for motion relative to its reel carrier in directions transverse to said axes, each of said nut members being engaged with one of the other two lead screws to translate rotation of its lead screw into motion of the reel carrier in the directions of said axes;

D. a drive motor; and

E. transmission means coupling said drive motor with all three lead screws to constrain each lead screw to rotate at a speed which is in a predetermined C. means constraining the reel carriers to move with the table in directions parallel to said axes. l0

2. The apparatus of claim 1 wherein said supporting means for the table and reel carriers comprises frame means having opposite upright sides overlain by the reel carriers, further characterized by:

A. cooperating shaft and bushing means carried by each reel carrier and by the frame means at said sides thereof, said shaft means being parallel to said axes and said shaft and bushing means cooperating to mount each reel carrier on the frame means for translatory motion in directions parallel to said axes and for swinging motion about an axis which is spaced above the center of gravity of the reel carrier and to that side of said center of ratio to the rotational speed of each of the others. gravity which is nearer the table; 4. The apparatus of claim 1 wherein said means con- B. cooperating rail and roller means carried by each straining the reel carriers to move with the table comreel carrier and by the frame means and spaced a prises: I substantial distance below the center of gravity of mans f Fomrouably dnvmg h table the reel carrier, posite directions transverse to said direction of 1. said rail means defining an elongated substan- Strip advancei,

tiany pane Surface which extends in the B. means for driving each of the reel carriers in opdirections of Said axes and which faces in one posite directions transverse to said direction of direction of swinging motion of the reel carrier, smp advance; and

C. means for s nchronrzin the drive means for each and said roller means being rolling), engaged with of the reel carriers with the drive means for the tathe rail means to define a limit of Swinging ble, to constrain the reel carriers to move in said tion of the reel carrier towards which the reel PPF difections substantially in unison with carrier is gravity Masai motion in said directions of the table.

3. The apparatus of claim 1 wherein said means con- 

1. Apparatus for processing strip material having defined lengthwise adjacent frames, which apparatus comprises a horizontal table mounted for horizontal translatory motion in all directions and having a defined area with which a frame of strip material registers for processing, means for lengthwise advancing strip material flatwise across said area of the table from one to another of a pair of reels, and means for releasably constraining a portion of strip material that comprises a frame registering with said area to move with the table, said apparatus being characterized by: A. a pair of reel carriers, one for each reel; B. means supporting the table and the reel carriers with the table elevated and with the reel carriers extending downwardly to a level substantially below that of the table and spaced to opposite sides of the table so that the table and the reel carriers are spaced apart in directions parallel to that of strip advance, said supporting means providing for
 1. horizontal translatory motion of the table in all directions,
 2. rotation of the reels on horizontal axes transverse to said direction of strip advance, and
 3. translatory motion of the reel carriers in opposite directions parallel to said axes; and C. means constraining the reel carriers to move with the table in directions parallel to said axes.
 1. Apparatus for processing strip material having defined lengthwise adjacent frames, which apparatus comprises a horizontal table mounted for horizontal translatory motion in all directions and having a defined area with which a frame of strip material registers for processing, means for lengthwise advancing strip material flatwise across said area of the table from one to another of a pair of reels, and means for releasably constraining a portion of strip material that comprises a frame registering with said area to move with the table, said apparatus being characterized by: A. a pair of reel carriers, one for each reel; B. means supporting the table and the reel carriers with the table elevated and with the reel carriers extending downwardly to a level substantially below that of the table and spaced to opposite sides of the table so that the table and the reel carriers are spaced apart in directions parallel to that of strip advance, said supporting means providing for
 1. horizontal translatory motion of the table in all directions,
 1. said rail means defining an elongated substantially plane surface which extends in the directions of said axes and which faces in one direction of swinging motion of the reel carrier, and
 2. said roller means being rollingly engaged with the rail means to define a limit of swinging motion of the reel carrier towards which the reel carrier is gravity biased.
 2. The apparatus of claim 1 wherein said supporting means for the table and reel carriers comprises frame means having opposite upright sides overlain by the reel carriers, further characterized by: A. cooperating shaft and bushing means carried by each reel carrier and by the frame means at said sides thereof, said shaft mEans being parallel to said axes and said shaft and bushing means cooperating to mount each reel carrier on the frame means for translatory motion in directions parallel to said axes and for swinging motion about an axis which is spaced above the center of gravity of the reel carrier and to that side of said center of gravity which is nearer the table; B. cooperating rail and roller means carried by each reel carrier and by the frame means and spaced a substantial distance below the center of gravity of the reel carrier,
 2. rotation of the reels on horizontal axes transverse to said direction of strip advance, and
 3. translatory motion of the reel carriers in opposite directions parallel to said axes; and C. means constraining the reel carriers to move with the table in directions parallel to said axes.
 3. The apparatus of claim 1 wherein said means constraining the reel carriers to move with the table comprises: A. three lead screws, each constrained to rotation and each extending parallel to said axes; B. a nut connected with the table to move therewith in the directions of said axes and cooperating with one of said lead screws to impart motion to the table in said directions in consequence of rotation of said one lead screw; C. a nut member carried by each of said reel carriers, each of said nut members being constrained to move with its reel carrier in the directions of said axes but being free for motion relative to its reel carrier in directions transverse to said axes, each of said nut members being engaged with one of the other two lead screws to translate rotation of its lead screw into motion of the reel carrier in the directions of said axes; D. a drive motor; and E. transmission means coupling said drive motor with all three lead screws to constrain each lead screw to rotate at a speed which is in a predetermined ratio to the rotational speed of each of the others. 